It had previously been shown that subchondral bone stiffening occurred in association with the earliest degenerative changes of articular cartilage in osteoarthrosis. Experiments are proposed to study in vivo the temporal relationship between the bone and cartilage changes in osteoarthrosis, the changes in trabecular organization and mechanical properties of the bone during this temporal sequence and to compare the experimental changes in the animals with the osteoarthrosic changes in cartilage and bone of humans.